FIG. 1 is a schematic perspective view illustrating a portion of the structure of a conventional laser module. The conventional laser module 1 has a TO-CAN package structure. Moreover, the conventional laser module 1 comprises a casing 11, a base 12, a laser diode 13, a photodiode 14, a heat sink 15, a first pin 16 and a second pin 17. The heat sink 15 and the photodiode 14 are fixed on the base 12. The laser diode 13 is disposed on the heat sink 15. The laser diode 13 and the photodiode 14 are connected with the first pin 16 and the second pin 17 through wires 18 and 19, respectively. The first pin 16 and the second pin 17 are penetrated downwardly through the base 12 and protruded outside. After the first pin 16 and the second pin 17 are penetrated through perforations of an external circuit board (not shown) and welded on the circuit board, electronic signals can be transmitted between the laser module 1 and the circuit board.
Moreover, the casing 11 is disposed on the base 12. The laser diode 13, the photodiode 14 and the heat sink 15 are covered by the casing 11. The casing 11 has an opening 111. A collimator lens 10 is disposed in the opening 111. After the laser diode 13 receives electric power through the first pin 16, the laser diode 13 provides a laser beam L1. The greater portion L11 of the laser beam L1 is propagated in the direction toward the opening 111 of the casing 11, transmitted through the collimator lens 10, and projected out. The smaller portion L12 of the laser beam L1 is projected on the photodiode 14 and optically detected by the photodiode 14. During the detecting process, the photodiode 14 generates detecting signals. These detecting signals are transmitted to the external circuitry through the second pin 17. According to the detecting signals, the subsequent controlling processes will be performed.
Moreover, for welding the laser module 1 on the circuit board, the laser module 1 should be additionally equipped with the first pin 16 and the second pin 17. The first pin 16 and the second pin 17 have to be penetrated through the circuit board. Generally, the sizes of these pins need to be greater than a lowest limit. If these pins are smaller than the lowest limit, the pins are readily broken in response to an external force. Since the package structure of the laser module 1 cannot be effectively minimized, the applications of the laser module 1 on a handheld device, a wearable device or any other small-sized electronic device will be reduced.
Moreover, when the optical element (e.g. the collimator lens 10) is integrated into the conventional laser module 1, the structure of the optical element occupies a large space. Consequently, the structure of the optical element is also detrimental to miniaturization of the conventional laser module 1. Moreover, the conventional laser module 1 is usually equipped with a single light source. Consequently, the conventional laser module 1 cannot comply with the requirements of plural light sources or plural wavelengths of the modern electronic device. Under this circumstance, the development of the handheld device, the wearable device or the comparable electronic device is restricted. In other words, the conventional laser module 1 needs to be further improved.